N-Doped Yellow TiO2 Hollow Sphere-Mediated Visible-Light-Driven Efficient Esterification of Alcohol and N-Hydroxyimides to Active Esters.

Herein we report a simple synthetic protocol for N-doped yellow TiO2 (N-TiO2 ) hollow spheres as an efficient visible-light-active photocatalyst using aqueous titanium peroxocarbonate complex (TPCC) solution as precursor and NH4 OH. In the developed strategy, the ammonium ion of TPCC and NH4 OH acts as nitrogen source and structure-directing agent. The synthesized N-TiO2 hollow spheres are capable of promoting the synthesis of active esters of N-hydroxyimide and alcohol through simultaneous selective oxidation of alcohol to aldehyde followed by cross-dehydrogenative coupling (CDC) under ambient conditions upon irradiation of visible light. It is possible to develop a novel and cost-effective one-pot strategy for the synthesis of important esters and amides on gram scale using the developed strategy. The catalytic activity of N-TiO2 hollow spheres is much superior to that of other reported N-TiO2 samples as well as TiO2 with varying morphology.

Novel nanocomposite derived from ZnO/CdS QDs embedded crosslinked chitosan: An efficient photocatalyst and effective antibacterial agent.

A novel nanocomposite (cl-Ch-pMAc@ZnO/CdSQDs) has been developed under microwave irradiation via fabrication of ZnO/CdS quantum dots on anionically functionalized chitosan [i.e. poly (methacrylic acid) crosslinked chitosan (cl-Ch-pMAc) in the presence of diethylene glycol dimethacrylate (DEGDMA) crosslinker]. The structural, morphological and chemical/physical properties of crosslinked chitosan and the nanocomposites have been investigated using 13C nuclear magnetic resonance spectroscopy (13C NMR spectroscopy), high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analyses. The nanocomposite demonstrates outstanding efficacy towards the photocatalytic degradation of cationic dyes [malachite green (MG), and safranin (SF)] and toxic organic molecule 2,4-dichloro phenol (2,4-DCP) under the exposure of sunlight. Liquid chromatography mass spectroscopy (LC-MS) studies predict that small molecules are produced by degradation. Moreover, the composite exhibits excellent antibacterial activity towards E-coli and B. subtilis. Finally, the nanocomposite can be regenerated effectively with changing the solution pH and also shows 5 times reusability without significant reduction on its efficiency.

Enhanced Thermocatalytic Activity of Porous Yellow ZnO Nanoflakes: Defect- and Morphology-Induced Perspectives.

Herein, we report a simple and effective strategy for the synthesis of yellow ZnO (Y-ZnO) nanostructures with abundant oxygen vacancies on a large scale, through the sulfidation of ZnO followed by calcination. The developed strategy allows retention of the overall morphology of Y-ZnO compared with pristine ZnO and the extent of oxygen vacancies can be tuned. The influence of oxygen deficiencies, the extent of defect sites, and the morphology of ZnO on its solution-phase thermocatalytic activity has been evaluated in the synthesis of 5-substituted-1H-tetrazoles with different nitriles and sodium azide. A reasonable enhancement in the reaction rate was achieved by using Y-ZnO nanoflakes (Y-ZnO NFs) as a catalyst in place of pristine ZnO NFs. The reaction was complete within 6 h at 110 °C with Y-ZnO NFs, whereas it took 14 h at 120 °C with pristine ZnO NFs. The catalyst is easy to recycle without a significant loss in catalytic activity.

Visible-light-driven Efficient Photocatalytic Reduction of Organic Azides to Amines over CdS Sheet-rGO Nanocomposite.

CdS sheet-rGO nanocomposite as a heterogeneous photocatalyst enables visible-light-induced photocatalytic reduction of aromatic, heteroaromatic, aliphatic and sulfonyl azides to the corresponding amines using hydrazine hydrate as a reductant. The reaction shows excellent conversion and chemoselectivity towards the formation of the amine without self-photoactivated azo compounds. In the adopted strategy, CdS not only accelerates the formation of nitrene through photoactivation of azide but also enhances the decomposition of azide to a certain extent, which entirely suppressed formation of the azo compound. The developed CdS sheet-rGO nanocomposite catalyst is very active, providing excellent results under irradiation with a 40 W simple household CFL lamp.

Visible-Light-Induced Efficient Selective Oxidation of Nonactivated Alcohols over {001}-Faceted TiO2 with Molecular Oxygen.

In the presence of molecular oxygen, a {001}-faceted nanocrystalline anatase TiO2 catalyst enabled the selective oxidation of nonactivated aliphatic alcohols to the corresponding aldehydes or ketones under visible light. The reaction shows excellent conversion and selectivity towards the formation of the carbonyl products without over-oxidation to the corresponding carboxylic acids. The exceptional reactivity of the catalyst is possibly due to the absorption of visible light originating from a stronger interaction of alcohol with the {001} facet, which facilitates the modification of the band structure of TiO2 , thus facilitating the photogenerated hole transfer and subsequent oxidation processes. The experimental results have also been corroborated by first-principles quantum chemical DFT calculations.

pH triggered superior selective adsorption and separation of both cationic and anionic dyes and photocatalytic activity on a fully exfoliated titanate layer-natural polymer based nanocomposite.

A fully exfoliated titanate layer-natural polymer amylopectin based nanocomposite, with pH responsive superior selective adsorption, separation of both cationic (MB: 599 mg g(-1) at pH 9) and anionic (MO: 558 mg g(-1) at pH 3) dyes and photodegradation properties, has been realized through simultaneous in situ layered titanate formation, exfoliation and polymerization.

Stimulus-Responsive, Biodegradable, Biocompatible, Covalently Cross-Linked Hydrogel Based on Dextrin and Poly(N-isopropylacrylamide) for in Vitro/in Vivo Controlled Drug Release.

A novel stimulus-sensitive covalently cross-linked hydrogel derived from dextrin, N-isopropylacrylamide, and N,N'-methylene bis(acrylamide) (c-Dxt/pNIPAm), has been synthesized via Michael type addition reaction for controlled drug release application. The chemical structure of c-Dxt/pNIPAm has been confirmed through Fourier transform infrared (FTIR) spectroscopy and (1)H and (13)C NMR spectral analyses. The surface morphology of the hydrogel has been studied by field emission scanning electron microscopic (FE-SEM) and environmental scanning electron microscopic (E-SEM) analyses. The stimulus responsiveness of the hydrogel was studied through equilibrium swelling in various pH media at 25 and 37 °C. Rheological study was performed to measure the gel strength and gelation time. Noncytotoxicity of c-Dxt/pNIPAm hydrogel has been studied using human mesenchymal stem cells (hMSCs). The biodegradability of c-Dxt/pNIPAm was confirmed using hen egg lysozyme. The in vitro and in vivo release studies of ornidazole and ciprofloxacin imply that c-Dxt/pNIPAm delivers both drugs in a controlled way and would be an excellent alternative for a dual drug carrier. The FTIR, powder X-ray diffraction (XRD), and UV-vis-near infrared (NIR) spectra along with the computational study predict that the drugs remain in the matrix through physical interaction. A stability study signifies that the drugs (ornidazole ∼97% and ciprofloxacin ∼98%) are stable in the tablet formulations for up to 3 months.

Efficient photocatalytic selective nitro-reduction and C-H bond oxidation over ultrathin sheet mediated CdS flowers.

We report here a visible light driven selective nitro-reduction and oxidation of saturated sp(3) C-H bonds using ultrathin (0.8 nm) sheet mediated uniform CdS flowers as catalyst under a household 40 W CFL lamp and molecular oxygen as oxidant. The CdS flowers were synthesized using a simple surfactant assisted hydrothermal method.

Dextrin and poly(acrylic acid)-based biodegradable, non-cytotoxic, chemically cross-linked hydrogel for sustained release of ornidazole and ciprofloxacin.

Herein, novel biodegradable, stimulus-responsive, chemically cross-linked and porous hydrogel has been synthesized to evaluate its applicability as an efficient carrier for sustained release of ornidazole and ciprofloxacin. The cross-linked hydrogel (c-Dxt/pAA) has been developed from dextrin and poly(acrylic acid) using N,N'-methylene bis(acrylamide) cross-linker via Michael-type addition reaction. With the variation of reaction parameters, various c-Dxt/pAA hydrogels have been synthesized to optimize the best one. c-Dxt/pAA hydrogel has been characterized using various physicochemical characterization techniques. The hydrogel demonstrates significant pH and temperature sensitivity. Gel characteristics and gel kinetics have been performed through the measurement of rheological parameters. The hydrogel shows noncytotoxic behavior toward human mesenchymal stem cells. Biodegradation study predicts that c-Dxt/pAA is degradable in nature. The in vitro release of ornidazole and ciprofloxacin suggests that the hydrogel released both the drugs in a controlled manner with extensive stability up to 3 months. The results suggest that c-Dxt/pAA is probably a promising candidate for controlled release of ornidazole and ciprofloxacin.

Chitosan derivatives cross-linked with iodinated 2,5-dimethoxy-2,5-dihydrofuran for non-invasive imaging.

Radiopaque polymer derivatives were successfully prepared through surface diffusion mediated cross-linking of chitosan with iodinated 2,5-dimethoxy-2,5-dihydrofuran. The incorporation of iodine in 2,5-dimethoxy-2,5-dihydrofuran was validated by (1)H NMR and mass spectroscopy. The cross-linking of the glucosamine moieties of chitosan with the iodinated product was confirmed by (13)C NMR and energy-dispersive X-ray spectroscopy. Radiography analysis proved inherent opacity of the iodinated fibrous sheets and microspheres that were comparable to the X-ray visibility of aluminum hollow rings of equivalent thickness and commercially available radiopaque tape, respectively. Microscopic studies evidenced retention of the fiber/microsphere morphology after the iodination/cross-linking reactions. The effects of iodination/cross-linking on the mechanical and biodegradation properties of fibers were studied by nanoindentation and enzymatic assay, respectively. In vitro and in vivo studies established the nontoxic, biodegradable nature of radiopaque derivatives. Iodinated fiber mesh implanted in a rabbit model was significantly X-ray opaque compared to the uncross-linked fiber mesh and medical grade surgical swabs. Further, opacity of the iodinated mesh was evident even after 60 days, though the intensity was reduced, which indicates the biodegradable nature of the iodinated polymer. The opacity of the iodinated sutures was also established in the computed tomography images. Finally, the sufficient in vivo contrast property of the radiopaque microspheres in the gastrointestinal tract indicates its possible role in clinical diagnostics.

Fluoride free synthesis of anatase TiO2 nanocrystals with exposed active {001} facets.

A novel fluoride free protocol for highly truncated anatase TiO2 nanocrystals with exposed {001} facets by preferential adsorption of CO3(2-) ions is developed. Experimental observations were corroborated by first principle quantum chemical DFT calculations. The synthesized anatase TiO2 showed improved photocatalytic activity.

Heterogeneously porous γ-MnO2-catalyzed direct oxidative amination of benzoxazole through C-H activation in the presence of O2.

Oxidative amination of azoles through catalytic C-H bond activation is a very important reaction due to the presence of 2-aminoazoles in several biologically active compounds. However, most of the reported methods are performed under homogeneous reaction conditions using excess reagents and additives. Herein, we report the heterogeneous, porous γ-MnO2-catalyzed direct amination of benzoxazole with wide range of primary and secondary amines. The amination was carried under mild reaction conditions and using molecular oxygen as a green oxidant, without any additives. The catalyst can easily be separated by filtration and reused several times without a significant loss of its catalytic performance. Of note, the reaction tolerates a functional group such as alcohol, thus indicating the broad applicability of this reaction.

Enhanced removal of methylene blue and methyl violet dyes from aqueous solution using a nanocomposite of hydrolyzed polyacrylamide grafted xanthan gum and incorporated nanosilica.

The synthesis and characterization of a novel nanocomposite is reported that was developed as an efficient adsorbent for the removal of toxic methylene blue (MB) and methyl violet (MV) from aqueous solution. The nanocomposite comprises hydrolyzed polyacrylamide grafted onto xanthan gum as well as incorporated nanosilica. The synthesis exploits the saponification of the grafted polyacrylamide and the in situ formation of nanoscale SiO2 by a sol-gel reaction, in which the biopolymer matrix promotes the silica polymerization and therefore acts as a novel template for nanosilica formation. The detailed investigation of the kinetics and the adsorption isotherms of MB and MV from aqueous solution showed that the dyes adsorb rapidly, in accordance with a pseudo-second-order kinetics and a Langmuir adsorption isotherm. The entropy driven process was furthermore found to strongly depend on the point of zero charge (pzc) of the adsorbent. The remarkably high adsorption capacity of dyes on the nanocomposites (efficiency of MB removal, 99.4%; maximum specific removal Qmax, 497.5 mg g(-1); and efficiency of MV removal, 99.1%; Qmax, 378.8 mg g(-1)) is rationalized on the basis of H-bonding interactions as well as dipole-dipole and electrostatic interactions between anionic adsorbent and cationic dye molecules. Because of the excellent regeneration capacity the nanocomposites are considered interesting materials for the uptake of, for instance, toxic dyes from wastewater.

Guar gum and guar gum-oligomeric poly(vinyl alcohol) blends as novel flocculants for kaolinated waste water.

This is probably the first report on kaolin flocculation done with aqueous guar gum (GG) at various pH. Dynamic light scattering and reduced viscosity proved the polyelectrolytic feature (zeta potential) of aqueous GG which changed on changing pH. Interestingly, the molecular size of GG did not always increased with rising zeta potential due to strong intermolecular repulsion leading to macromolecular recoiling. Best pH range for settling was 4.0-5.0 which included isoelectric point (IEP) of kaolin. Post-settling turbidity was also acceptable at that range. Optimized GG was further blended with oligomeric poly (vinyl alcohol) (PVA) (Mn 14,000) to prepare a new set of flocculant. Oligomeric PVA was previously optimized at similar pH as excellent kaolin flocculant in our earlier investigation. All GG-PVA blends including neat GG exhibited faster settling than neat PVA. However, settling times of all blend compositions were slightly greater than that of neat GG except for few cases where the post settling turbidity was found significantly lower than all our previous investigations.

Acrylic acid grafted guargum-nanosilica membranes for transdermal diclofenac delivery.

Green, hydrophobic device for controlled transdermal release of diclofenac sodium was designed from in situ nanosilica/acrylic acid grafted guargum membranes. Best grafting condition was assigned and nanocomposites were formed in situ using varying proportions of aqueous nanosilica sol. Nanocomposite/drug conjugates were formed by bringing down the medium pH from 9.0 to 7.0. The conjugates were characterized through infrared and solid state NMR spectroscopy, electron microscopy, hydro-swelling, surface contact angle, viscometry and biocompatibility. Most balanced property was exhibited by the membrane containing 1wt% nanosilica. It also had shown the highest encapsulation efficacy vis-à-vis slowest release as compared to others during experimentation in a Franz diffusion cell.

Novel biodegradable nanocomposite based on XG-g-PAM/SiO2: application of an efficient adsorbent for Pb2+ ions from aqueous solution.

This article highlights the development of a novel nanocomposite based on nanosilica filled modified natural polymer (i.e. xanthan gum grafted with polyacrylamide:XG-g-PAM) for removal of Pb(2+) ions from aqueous solution. The chemical, structural, textural, and rheological characteristics of the nanocomposite (XG-g-PAM/SiO(2)) revealed stronger interaction of silica nanoparticles with polymer matrix and showed maximum adsorption capacity (Q(max)=537.634 mg g(-1)) of Pb(2+) ion, which is significantly higher than other reported adsorbents. This developed novel material also finds potential application as an efficient adsorbent for the treatment of battery industry wastewater. The enhanced adsorption efficiency may be because of its higher hydrodynamic radius and hydrodynamic volume. The adsorption kinetic parameters were best described by pseudo-second-order model. The adsorption equilibrium data fitted well with Langmuir isotherm. The thermodynamic studies confirm that the adsorption is spontaneous and endothermic. Desorption studies affirmed the regenerative efficacy of loaded Pb(2+).

Onion slice shaped assembled ZnS quantum wires.

Ultra-narrow wurtzite ZnS quantum wires assembled towards an onion slice shape are synthesized in water using a simple hydrothermal procedure. Wires are formed through an oriented attachment mechanism from wurtzite ZnS spherical particles. Strong confinement effect originated from the narrow width was observed and holds promise for use in broad optoelectronic device application.

Room temperature synthesis of protonated layered titanate sheets using peroxo titanium carbonate complex solution.

We report the synthesis of peroxo titanium carbonate complex solution as a novel water-soluble precursor for the direct synthesis of layered protonated titanate at room temperature. The synthesized titanates showed excellent removal capacity for Pb(2+) and methylene blue. Based on experimental observations, a probable mechanism for the formation of protonated layered dititanate sheets is also discussed.

Synthesis, assembly, and optical properties of shape- and phase-controlled ZnSe nanostructures.

Shape-, size-, and phase-controlled ZnSe nanostructures were synthesized by thermolysis of zinc acetate and selenourea using liganding solvents of octadecylamine (ODA) and trioctylphosphineoxide (TOPO) at different molar ratios. Materials synthesized in pure ODA resulted in uniform ultranarrow nanorods and nanowires of 1.3 nm in diameter. Morphological change from nanowire to spherical particle of larger diameter occurs with increasing TOPO/ODA ratio. Variation of the TOPO content in the mixed solvent also allows control of the crystallographic phase of ZnSe (wurtzite or zinc blende). The conditions and mechanisms of shape and phase control are discussed. Ultra-high-density networks of the ordered wires are achieved using the Langmuir-Blodgett technique in a single step as an essential stage on the route to ultra-high-density semiconductor nanocircuit fabrication.